stilley



p 1963 H, H. STILLEY LIFT BUCKET ASSEMBLY 2 Sheets-Sheet 1 Filed April 18. 1960 INVENTOR HERSCHEL H. STILLEY BY ATTORNEYS Sept. 24, 1963 H. H. sTlLLEY LIFT BUCKET ASSEMBLY 2 Sheets-Sheet 2 Filed April 18, 1960 INVENTOR. HERSCHEL H. STILLEY ATTORNEYS.

United States Patent 3,104,771 LET BUCKET ASSEMBLY Herschel H. Stiliey, St. Joseph, Mich, assignor to Clark Equipment Company, a corporation of Michigan Filed Apr. 18, 1969, Ser. No. 22,731 11 Claims. (ill. 214-140) The present invention relates to improvements in lift bucket assemblies, and more particularly to assemblies of the class noted having improved lift height and reaching characteristics.

It is desirable in lift bucket assemblies, conventionally mounted at one end of bucket supporting means usually including supporting arms p-ivotally mounted on a tractor or other like type of vehicle, to provide for raising of the bucket to as great a height as possible. This is of importance, for example in loading material into a truck at one level by means of a tractor shovel or the like working on a lower level, as in a pit. It is also .advan tageous to obtain a long reaching action of the bucket so as to increase the dumping range and reduce positional maneuvering of the equipment.

The present invention provides a novel and improved structure for so pivotally mounting a lift bucket that maximum lift and reach are achieved.

It is an object of the invention to provide a lift bucket assembly which affords maximum lift height and maximum reach for the bucket.

Another object is the provision of a lift bucket assembly by which the bucket in dumping thereof in elevated position is tilted in such manner as not to extend substantially below the level to which it has been raised in its material-carrying position.

Another object is the provision of a lift bucket assembly in which the dumping movement of the bucket includes a forward or outward reaching movement from the raised material-carrying position of the bucket to increase the spacing of the dumping point from the lifting means.

A further object is the provision of .a lift bucket assembly including a parallelogram-type mounting linkage for the bucket which effects relative upward and forward movement of the bucket to ofiset downward and rearward tilting thereof in the dumping operation.

Other and further objects, advantages and features of the invention will be apparent to those skilled in the art from the following detailed description, taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a partial side elevational View of one embodiment of the invention, indicating different positions thereof; and

FIG. 2 is a vertical sectional view taken substantially as indicated by line 22 in FIG. 1, showing the bucket assembly in rear elevation, with certain parts broken away for greater clearness.

Referring to the drawing, there is shown a tractor, industrial truck, or similar powered mobile vehicle hav ing a pivot shaft 11 extending transversely thereof and projecting laterally therefrom on the outer ends of which are journaled a pair of upper lifting arms 12. Another transverse shaft 13 is carried by the vehicle 10, forwardly and downwardly spaced relative to the shaft 11, and having pivoted on its laterally projecting ends the rear ends of a pair of lower lifting arms 14. Both pairs of arms 12 and 14 are of such length that when in their lowermost positions they project forwardly of the tractor or other vehicle on which they are mounted, and each may be formed of a pair of parallel bars or plates, as best shown in FIG. 2. Means for raising and lowering the lifting arms are mounted on the vehicle 10, being shown as comprising at each side of the vehicle a hydraulic or like cylinder 15 with a piston rod 16, the cylinder being pivoted .as at 17 to suitable bracket means 18 secured on the vehicle, and the piston rod 16 being pivotally connected as at 19 to the adjacent arm 12. The upper and lower lifting arms 12 and 14 form part of a parallelogram-type linkage, being connected at their forward ends by a rigid mast structure generally designated 20 which forms a part of the lifting bucket assembly.

The mast structure 20 comprises a pair of upright members 2.1 each extending in the plane of the two arms 12 and 14 at one side of the vehicle. Each member 21 is formed of a pair of vertical plate members 22 spaced transversely of the adjacent arms 12 and 14 and arranged to receive the forward ends of the arms therebetween. The plates 22 are of a slightly bent formation in side elevation, as seen in FIG. 1, and project upwardly for a considerable distance above the forward ends of the adjacent arms 12, the lower ends thereof extending to the forward ends of the arms 14. The upper portions of the plates 22 of each member 21 are connected by a transverse web plate 23 welded or otherwise suitably secured thereto, and the upright members are joined at their central portions by a member 24 of box section. Extending transversely between each of the pairs of plates 22 is a pivot pin 25 theends of which are received in sleeves 26 projecting through the plates 22 and spaced somewhat below the lower end of the web plate 23. A hub 27 at the forward end of the adjacent arm 12 is journaled on the pin 25 between the sleeves. Another pin 25 is similarly arranged in sleeves 26 at the lower end of each of the upright members 22, to provide for the pivoting thereon by means of a hub 27 of the forward end of the adjacent arm 14.

A sleeve or hub 28 is secured as by welding at the upper end of each of the upright members 21 of the mast structure 29, for the reception of a pivot shaft 29 extending transversely between the members 21, with its ends projecting axially beyond the hubs 28. Upper links means comprising a pair .of link members 30 are pivoted by the pins 29 on the upright members 21. Each link member 30 is formed of a pair of link plates 31 each having a hub 32 at its upper end received on the shaft 29. A web plate 33 extends between and connects the upper portion of each pair of link plates 31, being welded or otherwise secured thereto.

A pair of lowerlinks 35 are pivoted on the mass structure, one on each of the upright members 21, at a level intermediate the axes of the pivot pins 25 of the arms 12 and 14, and normally extending downwardly. Each lower link '35 is pivoted by means of a hub 36 at its upper end extending transversely between aligned sleeves 37 projecting through the adjacent plate members 22, a pivot pin 38' extending through the hub and sleeves. Each link 35 is formed of a relatively heavy plate of suitable form the lower rearedge of which is adapted to engage a .stop block 39 secured at the lower end of the adjacent upright member 22. The other ends of the lower links 35, as well as the lower ends of the upper link members 30, are pivotally connected to a liftbucket as hereinafter described. It will be appreciated that the shafts 29 and 40, in addition to their pivoting function, serve to connect the upright members 21, supplementing the connecting member 24.

' A pivot shaft 40 extends transversely between the members 21, its ends being received in a pair of sleeves 41 each secured extending through the plate members 22 at approximately the level of the sleeves 3'7 but rearwardly thereof. Pivoted on the shaft 40 by means of lrub 42a, substantially centrally of the mast structure,

is a cylinder 42 the piston rod 43 of which is pivoted as by a hub 44 on a shaft 45 extending transversely of the upper link members 30 and having its end portions re ceived in sleeves 46 carried by the upper link plates 31.

By extending, collapsing, or holding fixed the extensible actuating means comprising the cylinder and piston rod, pivotal movement of the upper link members 30 on the upright members 21 can be controlled, and positioning of a lift bucket in desired tilted relation to the mast structure 20 thereby effected.

The lift bucket, generally designated 47, comprises a front wall 48, a rear wall 49, both substantially flat and angularly related to each other, and a curved bottom portion 50 connecting the front and rear walls. The bucket proper is completed by walls 51 closing the ends thereof. Adjacent the juncture of the front wall 48 and the bottom portion 50, a transverse strengthening and securing member 52 is secured, shown in this instance as an angle member with its flanges welded or otherwise securely fastened to the exterior of the bucket bottom 50. Two pairs of rigidifying and attaching ribs 53 are secured, as by welding, to the outside of the bucket substantially normal thereto, extending from the angle member 52 to adjacent the upper edge of the rear wall 49. Each pair of ribs 53 is located so as to receive within it the lower ends of one of the upper link members 3% and of the corresponding lower link 35 for pivotal connection thereto. A pivot pin 54 disposed in a hub 55 carried at the lower end of each upper link member 39* projects into bearing sleeves 56 secured projecting through the associated ribs 53. The upper link members are thus pivotally connected to the bucket. The lower links 35 are similarly pivoted to the bucket, each having at its lower end a hub 55 extending between sleeves 56 of the ribs 53 adjacent the lower or forward ends thereof, with a pivot pin 54 disposed in the aligned hub and sleeves.

Operating fluid from a suitable source, not shown, is supplied to and withdrawn from the opposite ends of the respective cylinderslS and 42 by means of suitable conduits 57 and 58, the flow of fluid being controlled by any known means, forming no part of the present invention.

It will be apparent that the mast structure 20 cooperates with the two pairs of lifting arms 12 and 14 to provide a parallelogram-type lifting linkage which alfords all the advantages of conventional linkages of this type, and that it also forms part of a second parallelogram-type linkage including the upper link members 30 and lower links 35 and the bucket 47. The latter linkage provides for the tilting of the bucket relative to the mast structure 20, by means of the cylinder 42,-to any desired position between one extreme position in which the bucket carries material and an opposite extreme position in which material is dumped from the bucket, in such fashion as to obtain maximum elevation and reach thereof.

In operation, the cylinders 15 are actuated to lower the arms 12 and therewith the arms 14, if they are not already lowered, to the full line position of FIG. 1, and the bucket 47 is brought to a desired digging or scooping position of which its full-line position is illustrative or exemplary. The positioning of the bucket is effected by the cylinder 42, the full-line position being achieved by bringing the piston rod 43 to a slightly projected position. The tractor, industrial truck, or other vehicle is then driven forwardly so that earth or other material loads the bucket 47, and the bucket is then brought to the dotted-line position indicated in FIG. 1 by fully retracting the piston rod 43, this being one extreme position of the bucket. This is the normal material-carrying position of the bucket, although material may be carried by the bucket in other positions if desired. Filling or loading of the bucket may be accomplished otherwise than as just described, depending upon the particular circumstances. For example, the bucket 47 may be swung upwardly by the lifting arms 12 and 14, either from the full-line position of FIG. 1 or a more elevated position, to pick up material from a heap, bank, or the like, and then brought to the carrying position. The disposition of the bucket in the carrying position may in any case be 5: accomplished by contraction of the extensible means provided by the cylinder and the piston rod while thebucket is being elevated by upward swinging of the lifting arms 12 and 14.

When the lifting arms have been swung to an elevated position, usually their extreme upper position, the bucket 47, in its material-carrying position, is ready for the dumping operation. This position of the parts is indicated in FIG. lin dot-dash lines. It will be noted that in the uppermost position of the parts, the mast structure 20 is tilted slightly rearwardly relative to its position in the loading position, but is still maintained substantially upright. The carrying position of the bucket is similarly changed slightly, but this only results in its being held more on a level than in the lower position. With the vehicle 10 driven to the location at which the bucket is to be emptied, the bucket is tilted to bring its forward edge to a level sufficiently below its bottom to assure that all of the material therein will fall out. This is done by extending the cylinder 42 and piston rod 43 so as to swing the upper link members 3! upwardly, thereby swinging the bucket forwardly or outwardly and at the same time turning it to effect dumping of the load therefrom. The dumping position of the bucket is indicated in dashdouble-dot lines. The projected piston rod 43 is then re tracted to return the bucket to its material-carrying position, or to a desired position intermediate its dumping and carrying positions, and the cylinders 15 and piston rods 16 are operated to lower the lifting arms 12 and 14,

and thereby the bucket 47. Such lowering of the bucket is ordinarily done after the tractor or like vehicle 10 has been moved back to the location of the material which is being moved, and loading and emptying may be-re peated as necessary. In the dumping or emptying action of the bucket'47, beginning with the position of the bucket and the associated linkage as shown in dot-dash lines, which as al- 7 ready mentioned indicates the elevated load-carrying posi tion, as the cylinder and piston are extended, the bucket is first tilted to lower the front wall to a substantially horizonal position, by the upward swinging of the lower ends of the upper link members 38. At the same time, due to the connections of the links 31 and 35 to the bucket and the action imparted to it as a result thereof, the

bucket is moved forwardly away from the mast structure 20. This intermediate position of the bucket is illustrated in double-dash-double dot lines in FIG. 1, and it will be obvious that the outward movement or reach of the bucket is very considerably greater than were it not provided with the linkage described and shown, and dumped merely by swinging downwardly from the load'carrying position. From theintermediate-position, the movement of the parts continues as the projection of piston rod 43 continues. As the upper link members 30 swing on upwardly, the bucket is raised, but due to the shorter links 35 connected to its bottom portion, the lower portionof the bucket is drawn inwardly or rearwardly and upwardly, so that the forward edge thereof is swung downwardly, and the bucket thus brought to the dumping or unloading position, shown in dash-double-dot lines in the figure. It is to be noted that by reason of the action resulting from the bucket linkage, the bucket is in effect raised as well as being moved forwardly or outwardly, While it is tilted or turned downwardly. Thus, the down ward turning movement of the forward edge thereof in the dumping movement is largely if not entirely counteracted or offset by the upward movement of the bucket, with the result that the forward edge of the bucket does not drop or move substantially below the level it assumed in the intermediate dottedline position, and only very slightly more below the load-carrying position of the in the lifting movement. Again, the added lift effected by the bucket linkage may be appreciated by comparing the unloading or dumping dash-double-dot line position of the bucket with the dumping position the bucket would assume if it merely pivoted downwardly from the raised load-carrying position.

It will acordingly be clear that the present invention provides a greatly improved lift bucket assembly affording important advantages in increased efiective lift and greater reach, thus resulting in a wider field of use of equipment employing the same and a reduction in the amount of maneuvering of such equipment necessary, with a corresponding increase in the proportion of working time devoted to actual loading of material, as distinguished from mere moving thereof between the points of bucket loading and bucket dumping.

It is to be understood that many changes and modifications may be made in the illustrated embodiment without departing from the invention, and that the invention is not to be limited except as required by the scope and spirit of the appended claims.

I claim:

1. In a tractor shovel construction comprising a powered vehicle having pivoted thereon parallelogramtype linkage including upper and lower pairs of lifting arms of lengths to dispose the forward ends thereof clear of the vehicle and power means for raising and lowering said arms, a bucket assembly comprising a generally upright mast structure extending transversely of said arms and projecting thereabove, means pivotally connecting the forward ends of the lower arms to the lower end of said mast structure, means pivotally connecting the forward ends of the upper arms to an intermediate portion of the mast structure, upper link means pivoted at an upper end thereof to the upper end of the mast structure, lower link means pivoted at an upper end thereof to the mast structure intermediate the axes of the pivotal connections of the upper and lower arms to the mast structure, a bucket having a front wall and a rear wall with a bottom therebetween, means pivotally connecting the upper link means at the other end thereof to said bucket along the height of the rear wall, means pivotally connecting the other end of the lower link means to the bucket adjacent the front wall and bottom, said upper link means being appreciably longer than said lower link means, a fluid-operable cylinder pivot-ally mounted on the mast structure having a piston rod pivotally connected to the upper link means at an intermediate portion thereof, and means for operating said cylinder to project and retract said piston rod, whereby the bucket may be tilted relative -to the mast structure between two extreme positions determined by the fully retracted and fully projected positions of said piston rod and the respective resultant positions of the upper and lower link means.

2. In a tractor shovel construction comprising a powered vehicle having pivoted thereon parallelogramtype linkage including upper and lower pairs of lifting arms of lengths to dispose the forward ends thereof clear of the vehicle and power means for raising and lowering said arms, a bucket assembly comprising a generally up right mast structure forming part of said linkage extending transversely of said arms and projecting thereab'ove, means pivotally connecting the forward ends of the lower arms to the lower end of said mast structure, means pivotally connecting the forward ends of the upper arms to an intermediate portion of the mast structure, upper link means pivoted at an upper end thereof to the upper end of the mast structure, lower link means pivoted at an upper end thereof to the mast structure intermediate the axes of the pivotal connections of the upper and lower arms to the mast structure, a bucket having a leading edge and a rear edge with a bottom there'between, means pivotally connecting the upper link means at the other end thereof to said bucket between the bottom and rear edge, means pivotally connecting the other end of the lower link means to the bucket between the leading edge and bottom, said mast structure, link means, and bucket defining a second parallelogram-type linkage, a fluid-operable cylinder for actuating said second linkage pivotally mounted on the mast structure having a piston rod pivotally connected to the upper link means at an intermediate portion thereof, and means for operating said cylinder to project and retract said piston rod, whereby the bucket may be tilted relative to the mast structure between two extreme positions determined by the fully retracted and fully projected positions of said piston rod and the respective resultant positions of the upper and lower link means.

3. In a tractor shovel construction comprising a powered vehicle having pivoted thereon parallelogram-type linkage including upper and lower pairs of lifting arms of lengths to dispose the forward ends thereof clear of the vehicle and power means for raising and lowering said arms, a bucket assembly comprising a generally upright mast structure extending transversely of said arm-s and projecting thereabove, means pivotally connecting the forward ends of the lower arms to the lower end of said mast structure, means pivotally connecting the forward ends of the upper arms to an inter-mediate portion of the mast structure, upper link means pivoted at an upper end thereof to the upper end of the mast structure, lower link means pivoted at an upper end thereof to the mast structure intermediate the axes of the pivotal connections of the upper and lower arms to the mast structure, a bucket having a rear wall, means pivotally connecting the upper link means at the other end thereof to said bucket along the rear wall, means pivotally connecting the other end of the lower link means to the bucket forwardly of the rear wall, extensible and contractible means disposed extending means at an intermediate portion thereof, and means for extending and contracting said extensible means whereby the bucket may be tilted relative to the mast structure between twoextreme positions determined by the fully contracted and fully extended positions of said extensible means and the respective resultant positions of the upper and lower link means.

4. In a tractor shovel construction comprising a powered vehicle having bucket lifting means thereon, a bucket assembly comprising a generally upright mast structure mounted on said lifting means for raising and lowering thereby, upper link means pivoted at an upper end thereof to the upper end of the mast structure, lower link means pivoted at an upper end thereof to a lower portion of the mast structure, a bucket, means pivotally connecting the upper link means at the other end thereof to said bucket adjacent the rear portion thereof, means pivotally connecting the other end of the lower link means to the bucket adjacent the front portion thereof, and poweroperated means mounted on the mast structure and con ne-cted to the upper link means for swinging said upper link means about said upper end pivotal means thereof, whereby the bucket may be tilted relative to the mast structure between two extreme positions determined by the limiting positions of said extensible means and the respective resultant positions of the upper and lower link means.

5. In a tractor shovel construction comprising a powered vehicle having pivoted thereon parallelogram-type linkage including upper and lower pairs of lifting arms and means for raising and lowering said arms, a lift bucket assembly comprising a bucket, 21 generally vertical mast structure pivotally connected to the upper and lower pairs of arms on vertically spaced horizontal axes, up per and lower link means respectively pivoted at one end to the mast structure on vertically spaced axes and at the other end to said bucket, said upper link means being pivoted to the bucket at the rear portion thereof and said lower link means being pivoted thereto forwardly of said rear portion and power means operatively connected between the mast structure and upper link means between the mast structure and the upper link for swinging the upper link means about the pivotal connection thereof to the mast structure.

6. A lift bucket assembly comprising a bucket having front and rear wall portions connected by a bottom portion, first relatively long link meanspivoted at one end thereof to said rear wall of the bucket, second relatively short link means pivoted at one end thereof adjacent the junction of said front wall and bottom portion, a mast structure arranged for generally upright disposition thereof and projecting appreciably above the level of the bucket, the other end of said first link means being pivoted to the upper end of said mast structure and the other end of said second link means being pivoted to the lower portion of the mast structure, and cylinder and piston means mounted on the mast structure and connected to the first link means for swinging movement thereof on the mast structure to effect tilting of the bucket.

7. A li fit bucket assembly comprising a bucket, first link means pivoted at one end thereof to the rear portion of the bucket, second link means pivoted at one end thereof adjacent the forward portion of the bucket, ta mast structure arranged for generally upright disposition thereof and projecting appreciably above the level of the bucket, the other end of said first link means being pivoted to an upper portion of said mast structure and the other end of said second link means being pivoted to a lower portion of the mast structure, and extensible and contracti-ble means mounted on the mast structure and connected to the first link means for swinging movement thereof on the mast structure to eflect tilting of the bucket.

8. A lift bucket assembly comprising a bucket having front and rear wall portions connected by a bottom portion, first relatively long link means pivoted at one end thereof to said rear wall of :the bucket, second relatively short link means pivoted at one end thereof adjacent the junction of said trout wall :and bottom portion, :a mast structure arranged for generally upright disposition there of and projecting appreciably above the level of the bucket, the other end of said first link means being pivoted to an upper portion of said mast structure and the other end of said second link means being pivoted to a lower portion of the mast structure, and extensible and contractible means mounted on the mast structure and connected to the first link means for swinging movement thereof on the mast structure to efiect tilting of the bucket, the relative lengths and pivot axes locations of said link means effecting forward projection of the bucket from a carrying position and an emptying rotation of the bucket from said projected position without material lowering thereof below the projected position, whereby maximum lift and reach is afiorded the bucket.

9. A tractor shovel construction comprising a powered vehicle, upper and lower pairs of lifting arms of lengths to dispose the forward ends thereof clear of the vehicle pivoted at the rear ends thereof on the vehicle, power means for raising and lowering said arms about the respective pivot axes thereof, a mast structure disposed in generally upright position projecting appreciably above said upper anrns and pivoted at its lower end to the forward ends of said lower arms and at an intermediate por-. tion to the forward ends of the upper arms, a bucket, upper link means pivoted at one end to the upper end of the mast structure and at the other end to the rear of said bucket, lower link means pivoted at one end to the mast structure on an axis intermediate the axes of the pivotal connections of the upper and lower arms thereto and pivoted at the other end to the bucket adjacent the forward portion thereof, and power means acting between the mast structure and upper link means to swing the link means .on the mast structure for effecting tilting of the bucket relative to the mast structure.

10. A tractor shovel construction comprising a pow ered vehicle, upper and lower pairs of lifting arms pivoted at the rear ends thereof on the vehicle, power means for raising and lowerng said arms about the respective pivot axes thereof, a mast structure disposed in generally upright position projecting appreciably above said upper arms and pivoted on substantially horizontal vertically spaced upper and lower axes respectively to the forward ends of said upper and lower arms, a bucket, upper and lower link means respectively pivoted at one end to the mast structure on vertically spaced axes and at the other end to the rear of said bucket and to the forward portion of the bucket, and power means acting between the mast structure and upper link means to swing the link means on the mast structure for effecting tilting of the bucket relative to the mast structure.

11. A tractor shovel construction comprising-a pow ered vehicle, bucket lifting means mounted on thevehicle,

a mast'structure disposed in generally upright position" mounted on said lifting means, a bucket, upper link means pivoted at one end to the upper end of the mast structure and at the other end to the rear of said bucket, lower link means pivoted at one end to a lower portion of the mast structure and at the other end to the bucket forwardly of the pivotal connection thereto of said upper link means, and power means acting between the-mast structure and upper link means to swing the link means on the mast structure for effecting tilting of the bucket relative to the mast structure to selected operating posi-j tions.

Sewell et al. July s, 1955 Christensen Apr. 23, 1957 Beyerstedt Mar. 22, 1960 i 

1. IN A TRACTOR SHOVEL CONSTRUCTION COMPRISING A POWERED VEHICLE HAVING PIVOTED THEREON PARALLELOGRAM-TYPE LINKAGE INCLUDING UPPER AND LOWER PAIRS OF LIFTING ARMS OF LENGTHS TO DISPOSE THE FORWARD ENDS THEREOF CLEAR OF THE VEHICLE AND POWER MEANS FOR RAISING AND LOWERING SAID ARMS, A BUCKET ASSEMBLY COMPRISING A GENERALLY UPRIGHT MAST STRUCTURE EXTENDING TRANSVERSELY OF SAID ARMS AND PROJECTING THEREABOVE, MEANS PIVOTALLY CONNECTING THE FORWARD ENDS OF THE LOWER ARMS TO THE LOWER END OF SAID MAST STRUCTURE, MEANS PIVOTALLY CONNECTING THE FORWARD ENDS OF THE UPPER ARMS TO AN INTERMEDIATE PORTION OF THE MAST STRUCTURE, UPPER LINK MEANS PIVOTED AT AN UPPER END THEREOF TO THE UPPER END OF THE MAST STRUCTURE, LOWER LINK MEANS PIVOTED AT AN UPPER END THEREOF TO THE MAST STRUCTURE INTERMEDIATE THE AXES OF THE PIVOTAL CONNECTIONS OF THE UPPER AND LOWER ARMS TO THE MAST STRUCTURE, A BUCKET HAVING A FRONT WALL AND A REAR WALL WITH A BOTTOM THEREBETWEEN, MEANS PIVOTALLY CONNECTING THE UPPER LINK MEANS AT THE OTHER END THEREOF TO SAID BUCKET ALONG THE HEIGHT OF THE REAR WALL, MEANS PIVOTALLY CONNECTING THE OTHER END OF THE LOWER LINK MEANS TO THE BUCKET ADJACENT THE FRONT WALL AND BOTTOM, SAID UPPER LINK MEANS BEING APPRECIABLY LONGER THAN SAID LOWER LINK MEANS, A FLUID-OPERABLE CYLINDER PIVOTALLY MOUNTED ON THE MAST STRUCTURE HAVING A PISTON ROD PIVOTALLY CONNECTED TO THE UPPER LINK MEANS AT AN INTERMEDIATE PORTION THEREOF, AND MEANS FOR OPERATING SAID CYLINDER TO PROJECT AND RETRACT SAID PISTON ROD, WHEREBY THE BUCKET MAY BE TILTED RELATIVE TO THE MAST STRUCTURE BETWEEN TWO EXTREME POSITIONS DETERMINED BY THE FULLY RETRACTED AND FULLY PROJECTED POSITIONS OF SAID PISTON ROD AND THE RESPECTIVE RESULTANT POSITIONS OF THE UPPER AND LOWER LINK MEANS. 